1. Field of the Invention
The present invention relates generally to a system and method for the detection of contraband and more particularly to a system and method for the detection of nuclear and related weapons material in shipping containers.
2. Description of the Prior Art
Every day, thousands of shipping containers enter the United States and other countries carried on large container ships. These containers are packed with goods in various foreign countries, loaded onto container ships and shipped into receiving ports in the US and elsewhere. According to one report, in the year 2002, more than 7500 commercial vessels made approximately 51,000 port calls offloading 6 million marine containers in U.S. Ports. Given the current climate, there exists a genuine fear that terrorists might smuggle nuclear material to make some sort of nuclear device or other weapon contraband in one or more of these containers.
It is well known that enough plutonium or enriched uranium to make a nuclear bomb fits in a relatively small space. It is also known that even smaller amounts of lesser enriched nuclear material could be used to make a so-called dirty bomb. The estimated amount of plutonium needed for an implosion device is around 25-30 kg; the amount of enriched uranium needed for a simple cannon device is around 40-60 kg (See Wikipedia Free Encyclopedia on the Internet). It is difficult to detect such small amounts of these materials.
At the present time, only cursory checks are made on containers coming off ships in the U.S. In fact, the U.S. government admits that, at the present time, only about 2% of the marine containers entering the country is checked. For example, in 2003 ABC News loaded 15 pounds (about 7.5 kg) of depleted uranium into a steel pipe which was packed in a suitcase in Jakarta. They put the suitcase into a teak trunk along with other furniture and shipped it to the U.S. in a marine shipping container. The uranium was never detected and successfully entered the U.S. Had this shipment contained enriched uranium or plutonium, the recipient would have had about ⅓ to ⅕ of the material needed to make a weapon
Various techniques have been developed in the prior art to “look inside” marine and other shipping containers. In particular x-ray machines and gamma ray detectors have been proposed, and also used, for checking containers. In Australia, customs officials report that they are currently x-raying approximately 80,000 containers a year. X-raying of baggage and hand-carry items at airports worldwide has become commonplace. U.S. Pat. No. 4,430,568 shows an early version of this type of x-ray system, while U.S. Pat. No. 5,247,561 shows an inspection system for closed containers. U.S. Pat. No. 6,661,867 shows a tomographic scanning x-ray inspection system, and U.S. published patent applications 2003/0215054 and 2004/0141584 show larger systems. These prior art systems cannot positively identify nuclear material with a high probability (or heavy lead or steel containers) and cannot generally correlate x-ray patterns with any other type of information.
It has also been reported that bills of lading and contents lists for containers are not always correct as to container contents, and that reported container count for a particular ship is not always correct. A container scanning system that can correlate and combine information from x-ray, gamma ray or other pattern detection with container tag information, imperfect bills of lading and content lists and any other available intelligence that might be available would be advantageous.